Grinding machine



Nov. 24, 1942. H. A. SILVEN GRINDING MACHINE Original Filed March 27, 1940 6 Sheets-Sheet l k 'l-|- 1. MN\ mw m Q Ill Ewen/bot HERBERT A. 5/1. VEN

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Nov. 24, 1942. H, SILVEN 2,302,915

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GRINDING MACHINE Original Filed March 27, 1940 6 Sheets-Sheet 5 Ill.

"HERBERT A. 51/. \/EN Original Filed March 27, 1940? 6 Sheets-Sheet 6 306 i is 307 I F 14 806 304 268 304 00 27/ 002 4 k 22 WHEEL UP I ii 47 g 47 5/ HERBERT A. 5/1. VEN

Patented Nov. 24, 1942 GRINDING MACHINE Herbert A. Silven, Worcester, Mass., assignor to Norton Company, Worcester, Mass, a corporation of Massachusetts Original application March 27, 1940, Serial No. 326,224, now Patent No. 2,284,073, dated May 1940, Serial No. 344,096

3 Claims.

The invention relates to grinding machines, and with regard to its more specific features to surface grinding machines. This application is a division of my application Serial No. 326,224, filed March 27, 1940, which has issued as U. S. Patent No. 2,284,073, dated May 26, 1942.

One object of the invention is to provide a a feed or wheel slide which is supported thereon hydraulically. Another object of the invention is to provide a fluid pressure system in which heat losses into the base are minimized. Another object of theinvention is to provide a vertical feed controlling and actuating mechanism which is susceptible of quick and accurate control automatically and manually and designed to operate according to the objects heretofore given. Other objects will be in part obvious or in part pointed out Hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings in which is il- Divided and this application July 5,

anism for feeding the grinding wheel in a vertical direction;

Fig. 5 is a fragmentary front elevation, on an enlarged scale, of the vertical wheel feedin mechanism and the controls therefor;

Fig. 6 is a fragmentary sectional view, on an enlarged scale, taken approximately on the line 66 of Fig. 5;

Fig. 7 is a fragmentary sectional view taken ap proximately on the line I-l of Fig. 6;

Fig. 8 is a fragmentary sectional view, on an enlarged scale, taken approximately on the line 8-8 of Fig. 6; I

Fig. 9 is a vertical sectional view taken approximately on the line 9-9 of Fig. 4;

Fig. 10 is a fragmentaryf vertical sectional view, on an enlarged scale, through the cross slide and the vertical slide, showing also part of the vertical column;

Fig. 11 is a fragmentary cross-sectional view taken approximately on the line I.I| I of Fig.'l0;

Fig. 12 is a fragmentary sectional view, on an enlarged scale, taken approximately on the line lZ-IZ of Fig.

Fig. 13 is a fragmentary vertical sectional view,

on an enlarged scale, taken approximately on the lustrated one of many possible embodiments of approximately 011 the line 3-3 of Fig. 5, illus trating the feeding mechanism to feed the grinding wheel in a vertical direction;

Fig. 4 is a fragmentary vertical sectional view,

, on an enlarged scale, taken approximately on the line 44 of Fig. 5, showing the feeding mech- 55 line i3-l3 of Fig. 1, showing the cross feeding mechanism; and

Fig. 14 is a fragmentary horizontal sectional view, taken approximately on the line l4l4 of Fig. 10.

A surface grinding machine has been illustrated in the drawings comprising a base 40 which supports a longitudinally reciprocable work 7 supporting table 4| on the usual V-way 42 and fiat way 43 formed on the upper surface of the base 40. The base 40 supports an upwardly projecting massive column 46 (Fig. 1) which is provided with a vertically xtending slideway 41. A vertically movable slide 48 is provided with ways which mate with the slideway 41 so that the slide 48 may be moved in a vertical direction. The vertically movable slide 48 is provided with a horizontally extending slideway 49 which serves as a support for a transversely movable wheel slide 50. In the preferred form an antifriction support is provided for the wheel slide 50 which may comprise anti-friction rollers 51 and 52 (Figs. 2 and 27) which are arranged at opposite ends of the wheel slide 50 and are supported thereon by means of the shafts 53 and 54, respectively. The rollers 5| and 52 ride upon the slideway 49 and serve as an anti-friction support for the slide 50. A plate 55 which is bolted to the wheel slide 50 by means of screws 58 (Fig.

2'!) serves to guide the wheel slide 80 and to hold it in position upon the slideway 49.

The lower portion of the vertical slide 48 is provided with a longitudinally extending flat way 51 which serves to support and guide the lower portion of the wheel slide 50. In order to provide an anti-friction support, the wheel slide is provided with anti-friction rollers 58 and 59 (Figs. 10 and 12) which are supported on shafts 80 and BI journalled in the wheel slide. A plate 62 which is bolted to the wheel slide 50 by screws 63 serves to prevent a lifting of the wheel slide and also serves as an additional means for guiding the wheel slide during its transverse movement. 4

In order to facilitate adjustment of the lower sliding elements, the rollers 58 and 50 are preferably supported by an anti-friction bearing and are formed integral with the studs 50 and BI but eccentric relative thereto. By a rotary adjustment of the studs 60 and 6|, the anti-friction rollers 58 and 59 may be adjusted as desired to take up any lost motion in the lower sliding part. A pair of lock nuts are provided for the studs 53, 54, and SI which serve to clamp them in adjusted positions. Outwardly extending end portions of the studs 53, 54, B0 and BI are formed of a square cross-sectional shape whereby the studs may be readily rotated by means of a wrench and when adjusted into the desired position may be locked by tightening the lock nuts.

The cross slide or wheel slide 50 serves as a support for a rotatable grinding wheel 65 which is supported at one end of a rotatable wheel spindle 66. The wheel spindle 58 is journalled in suitable bearings 61 which are mounted in fixed relation with the wheel slide 50. The bearings 61 are provided with the usual adjusting devices whereby the bearing may be adjusted to compensate for wear of the parts.

The grinding wheel spindle 86 may be driven by means of an electric motor 88 which is adjustably supported on a bracket depending from the wheel slide 50 (Fig. 10). The motor 68 is provided with a multiple V-groove pulley 89 which is connected by means of a multiple V- belt I0 with a multiple V-groove pulley II which is mounted on the end of the wheel spindle 68.

The motor 68 is supported on a vertically ad justable plate 12 (Fig. 10) which is adjustably supported on a depending slideway I3 formed integral with the wheel slide 50. An adjusting screw I4 is rotatably supported in a bracket I5 which is fixedly mounted on the depending portion of the wheel slide 50. The screw 14 is held against endwise movement in the bracket I5 but is arranged for a rotary movement relative thereto. The screw I4 is screw threaded into a portion I6 of the supporting plate 12 so that when the screw 14 is rotated, the screw will impart a vertical adjusting movement to the plate I2 and the motor 68 to facilitate adjusting the tension of the driving belt I0.

Hydraulic table traverse mechanism The work table H is traversed or reciprocated R longitudinally by means of a hydraulically op- -;.-erated table traversing mechanism comprising under side of the table 4I at its right-hand end (Fig. 2). Similarly the cylinder IOI contains a slidably mounted piston I05 which, is connected by means of a piston rod I08 with a bracket I01 depending from the under side of the table 4| at its left-hand end.

A table reversing valve H0 is provided to control the passage of fluid under pressure through a pipe III into a cylinder chamber II 2 within the cylinder I 0|, or through a pipe II3 into a cylinder chamber II 4 formed within the table cylinder I00. The reversing valve H0 is a piston type reversing valve comprising a valve stem the valve pistons H5, H1, H8, H9, I20, I2I, I22, and I23.

A fluid pressure system is provided for conveying fluid under pressure to the various mechanisms of the machine, comprising a reservoir I25 (Figs. 1 and 14) which is preferably formed within the box-like base 40 of the grinding machine. Fluid is pumped from the reservoir I25 by means of a motor driven fluid pressure pump I28 which draws fluid through a pipe I21 and forces the fluid under pressure through a pipe I20 into the valve chamber located between the valve pistons I20 and I2I. Fluid under pressure is also simultaneously passed from the pipe I28, through the pipe I28 (Fig. 3), into the valve chamber located between the valve pistons H8 and H9. In the position of the valve stem II5 (Fig. 2), fluid under pressure also enters the valve chamber between the valve pistons II! and H8. An adjustable relief valve I30 is connected in the pipe line I28 and serves to return excess fluid under pressure to the reservoir I25. Excess fluid under pressure within the pipe I28 serves to open the relief valve I30 and exhaust excess fluid under pressure through a pipe I3I into the reservoir I25.

A second motor driven fluid pressure pump I35 is provided for pumping fluid through a pipe I35 from the reservoir I 25 and forcing fluid under pressure through a pipe I31 into a valve chamber located between the valve pistons I2I and I22- and also to convey fluid under pressure from the pipe I31 through a pipe I38 into the valve chamber located between the valve pistons I I1 and I I8 (Fig. 2). The admission of fluid under pressure to the end chambers of the valve I I0 serves to aid in shifting the reversing valve into its reverse position. The fluid pressure pump I85, in addition to conveying fluid under pressure to aid in the shifting of the table reversing valve I I0, also serves to supply fluid under pressure to other fluid pressure operated mechanisms of the machine which will be hereinafter described. A relief valve I39 connected with the pipe line I31 serves to exhaust excess fluid under pressure through a pipe I40 into the reservoir I2I.

Reverse valve-actuating mechanism A reversing lever I44 (Fig. l) is mounted on the front of the machine base. The lever I44 is formed as a bell crank lever having outwardly projecting arms I45 and I46 which serve as supports for rotatably mounted rollers I41 and I48. The reversing lever I44 is flxedly mounted on the upper end of a rock shaft I49. The shaft I49 is arranged in a substantially vertical position and is supported in bearings I50 and I5I. The bearings I50 and I5I are in turn supported in a rotatable sleeve I 52 which is in turn rotatably supported within an aperture I53 formed within a table reversing apron I54 which H5 having formed integrally therewith v is fixedly mounted on theiront of the machin base 40. I

Start and stop valve In order to readily control the starting and stopping of the grinding cycle, a start and stop valve 205 (Figs. 3, 8 and 9) is provided. This valve 205 is a piston type valve comprising a valve stem 208 having formed integrally therewith valve pistons 201 and 208. A pipe 209 connecting with the valve chamber located between the valve pistons 2'01 and 208 (Figs. 3 and 8) is connected with'the pipe I I I which connects with the chamber located between the valve pistons II 8 and I I9 of the reversing valve IIO. A pipe 2I0 connects the end chambers of the stop and start valve 205 with the reservoir I25 so that any fluid within these chambers may readily exhaust into the reservoir. A pipe 2 is connected at one end to the chamber located between the valve pistons 201 and 208 of the stop and start valve 205 and connects with the pipe H8 (Fig. 3). A pipe 2I2 is connected between the stop and start valve 205 at one end and at the other end connects with the valve chamber located between the valve pistons H9 and I20 of the reversing valve I I0, so that in the position (Fig. 2) a manual traverse of the table H is facilitated by a by-passing of fluid between the cylinders I and I M.

1 Vertical feed A feeding mechanism is provided for moving the slide 48 vertically to adjust the position of the grinding wheel 65 relative to vthe work table 4| and the work piece to be ground. This mechanism may. comprise a rotatable feed screw 250 (Fig. 10) which is journalled at its upper and lower ends in anti-friction bearings 25I, 2'52. 258 and 254 which are in turn supported in the vertically extending column 46. A nut 255 mounted on the vertically movable slide 48 meshes with the screw 250.

In order to eliminate backlash between the screw 250 and the nut 255, a second nut 256 is provided which also meshes with or engages the feed screw 250. The nuts 255 and 258 are held in alignment with each other by means of a pair of pins or studs 251 and 258 (Figs. 10 and 11) which are arranged on diametrically opposite sides of the feed screw 250. The pins or studs 251 and 258 tightly fit holes within the nut 255 and slidably engage holes formed in the nut 258 so that the nut 258 is held in alignment with the nut 255 but is free to move in an endwise or axial direction. In order to take up the backlash between the screw 250 and the nut 255, the nuts 255 ranged in the path of the stud 28I. It the slide 48 and the nut 255 are raised above the upper end of the screw threads on the feed screw 250,

and 256 are urged in opposite directions so that to prevent the nuts 255 and 258 from moving.

endwise into engagement with the bearing supports. This is preferably accomplished by means of mounting a stud 28I in the upper surface of the nut 255. A collar 282 is adjustably clamped on a reduced upper end portion of the screw 250.

The collar 282 carries a stud 263 which ls'arthe stud 285 will rotate into engagement with the stud 26I and thus prevent further rotation of the feed screw 250.

Similarly, the lower nut 258 isprovided with a stud'284. A collar 285 is adjustably clamped on the lower reduced end portion of the feed screw 250. The collar 285 carries a stud 268 which is arranged in the path of the stud 264 so that in case the slide 48 is lowered so that the nut 258 approaches the end of the threads on the feed screw 250, the stud 288 will rotate into engagement with the fixed stud 264 and thus prevent further rotation of the. feed screw 250. A spiral gear 210 (Fig. 10) is keyed on the lower end of the feed screw 250. The spiral gear 210 meshes with a spiral gear 2" which is formed integral with a shaft 288 which is connected by means of a sleeve 289 to one end of a rotatable shaft 212 (Fig. 14). The shaft 288 is rotatably supported in bearings 3M and 302 (Fig. 18) in a housing 303 which is fixedly supported on the column 46. The shaft 212 (Fig. 3) extends horizontally within the base 40 and is rotatably supported in bearings 218 and 214 in the apron 281. A clutch plate 215 is fixedly mounted on the outer end of the shaft 212. The clutch plate 215 is provided with clutch teeth 'hich are arranged to be engaged by clutch teeth- 218 formed within a cup-shaped aperture within a slidably mounted rotatable gear 211 which is rotatably supported on the shaft 212.

In the position illustrated in Figs. 3 and 5, the .gear 211 meshes with a gear 218 which is supported on and keyed to the hub 219 of the index wheel 280. The index wheel 280 together with its integral hub 219 is rotatably supported on a stud 28I which is in turn fixedly mounted on the apron 281. A manually operable feed wheel 282 is rotatably supported on the forward end of the stud 28I and is connected by means of the, old and well known micrometer adjusting mechanism 283 with the index wheel 280. This micrometer adjusting mechanism will not be described in detail since this mechanism is a common expedient in cylindrical and surface grinding machines and is substantially the same as that shown in the prior U. S. patent to Norton, No. 762,838, dated June 14, 1908, to which reference may be had for details of disclosure not contained herein. It will be readily apparent from the foregoing disclosure that in the position of the parts (Figs. 3 and 10), any rotary movement of the hand wheel 282 will be transmitted to rotate the shaft 212 and spiral gear 2" which in turn transmits a rotary movement to the gear 210 and the feed screw 250 to raise or lower the nuts 255 and 258 and thus transmit a vertical movement or adjustment to the slide 48 to raise or lower the grinding wheel as desired.

A manually controlled means is provided for disconnecting the clutch teeth 215 and 218. The hub of the gear 211 is provided with a groove 285 which is engaged by a pair of diametrically opposed studs 288 carried by the yoked end of a lever 281. The lever 281 is pivotally supported on ,a stud 288. A lever 289 is also supported on the stud 288 and is preferably formed integral with the lever 281, the levers 281 and 289 operating as a bell crank lever. The forward end of the lever 289 is provided with a follower 290 (Figs. 3 and 4) which is arranged to engage a cam 29I which is rotatably supported on a shaft 292. A knob 293 serves to rotate the cam 29! so as to rock the bell crank levers 281-289 to move the Hydraulically operated lift for grinding wheel slide The wheel slide assembly, that is, the vertical slide 48 and the transversely movable wheel slide 50 carried thereby, are heavy, massive parts which would require considerable exertion on the part of the operator to raise and lower the same.

manually. It is desirable, therefore, to provide a power operated lifting mechanism which in the preferred form comprises a fluid motor 300 (Figs. 2 and 14). The fluid motor 300 is supported by a bracket 304 which is also fixedly supported on the rear of the column 48. The fluid motor 300 is preferably a rotary type motor such as, for example, that manufactured by Sundstrand Machine Tool Company of Rockford, Illinois. The rotor shaft of the motor 300 is provided with a gear 305 which meshes with a gear 306 supported at one end of a rotatable shaft 301. The shaft 301 is rotatably supported by a bracket mounted on the column 46. The shaft 301 is provided with a small gear 308 at its other end which meshes with a gear 309 which is keyed to the end of the shaft 268 supporting the spiral gear 21! (Fig. '14).

A control valve 310 is provided to control the admission of fluid under pressure to the fluid motor 300. The valve 3|0 (Fig. 9) is preferably a piston type valve comprising a valve stem 3!! having formed integrally therewith valve pistons 3!2, 3!3 and 3l4. The valve 3!0 is normally held in a central or neutral position by means of a spring 3 I 5.

The shaft 292 is preferably fixedly mounted in the apron 261 (Fig, 4). The shaft 292 supports a rotatable sleeve 3I8 to which is fixed the knob 293 and the cam 29!. The shaft 292 also rotatably supports a downwardly extending arm 3I9. The arm 3|9 carries a stud 320 which engages a groove 32! formed in a spool-shaped member 322 which is carried on the outer end of the valve stem 3!!. A lost motion connection is provided between a projection on the hub 323 of the lever 3!9 and the inner end of the sleeve 3!8. This lost motion connection is provided with sufficient lost motion so that when the knob 293 is rotated to cause an upward or downward movement of the wheel slide assembly, the cam 29! will rock the bell crank lever 289-281 to disengage the clutch teeth 215-216 before the valve stem 3|! is shifted to initiate a vertical movement of the wheel slide assembly.

A tension spring 325 is connected between a stud 326 supported in the periphery of the cam 29! and a stud which is carried by a bracket 32! fixed on the apron 261 which is fixedly mounted with respect to the base 40. The spring 325 normally tends to hold the cam 29! in position with the stud 290 engaging a notch 328 in the periphery of the cam 29! (Fig. 9), in which position the valve 3!0 is in a neutral or central position and the clutch 215-215 is in operative engagement so that a rotary movement of the hand wheel 282 will be transmitted through a key and keyway construction to rotate the ment to the gear 211 and also to the shaft 212.

When the knob 293 is rotated in a clockwise direction (Fig. 18) to rotate the cam 29! also in a clockwise direction into the position illustrated in Fig. 21, the bell crank lever 289-291 first disengages the clutch teeth 215-219 to disengage the hand wheel 282, after which the stud 320 on the downwardly extending arm 3! 9 shifts the valve stem 3!! toward theleft to shift a valve 3!0 to admit fluid under pressure to the fluid motor 300. Rotation of the motor 300 serves through the gear mechanism above described to rotate the vertical feed screw 250 to raise the wheel slide assembly in a vertical direction. As soon as the operator releases his grasp on the knob 293, the released tension of the spring 325 will rotate the cam 29! in a counterclockwise direction until the stud 290 engages the notch 328, thus returning the valve 3l0 into a neutral position (Fig. 9) and again connecting the clutch teeth 215-216.

Similarly when the knob 293 is rotated in a counterclockwise direction to shift the cam 29! also in a counterclockwise direction, the bell crank lever 289-281 first disengages the clutch parts 215-216 and then, through the arm 3H and stud 320, moves the valve stem 3!! toward the right to admit fluid under pressure to rotate the fluid motor 300 in the reverse direction. The

30 fluid motor 300, through the gear connections gear 218 which in turn transmits a rotary moveabove described, in turn rotates the feed screw 250 in the reverse direction to cause a downward feeding movement of the grinding wheel assembly. Similarly when the operator releases his grasp on the knob 293, the released tension of the spring 325 again rotates the cam 29! in a clockwise direction until the stud 290 engages the notch 328 in the periphery of the cam 29!, during which movement the valve M0 is again shifted into a central or neutral position (Fig. 9) and the clutch parts 215-216 are again engaged.

It will thus be seen that when it is desired to raise or lower the grinding wheel through a considerable distance in setting up the machine, a raising or lowering movement may readily be obtained by actuation of the control knob 293. Turning the knob 293 in a clockwise direction (Fig. 1) shifts the parts to start the fluid motor 300 to rotate the screw 250 and raise the grinding wheel assembly. Rotation of the knob 293 in a counterclockwise direction serves to start the fiuid motor 300 in the reverse direction to lower the grinding wheel assembly.

Automatic down feed In order that the improved surface grinding machine may be automatic in its cycle of operation, it is desirable to provide an automatic down feeding mechanism whereby the gxinding wheel 85 may be incrementally and automatically fed downwardly after the grinding wheel has been traversed completely across the reciprocating work piece to remove an additional amount of material from the surface of the work piece being ground during the next traverse of the grinding wheel 65 across the work as the work is reciprocated. A pivotally mounted feed arm 330 (Fig. 5) is pivotally supported by a stud 33!. The feed arm 330 supports a small gear 332 which is arranged to mesh with the gear 280 of the feed mechanism above described. The gear 332 is formed integral with a stud 333 which is rotatably supported by a sleeve 335. A ball clutch 334 is also supported on the stud 333 and is fixedly mounted relative to the gear 332. The arm 330 to be hereinafter described. The ball clutch 334- ment through the gear mechanisms above described to rotate the feed screw 253 and thereby cause a downward feeding movement of the grinding wheel 35. v

The sleeve 335 which surrounds the ball clutch 334 is provided with a projecting portion or shield 333 which surrounds a portion of the gear 332. The shield 333 is cut out on one side so as to allow the gear 332 to project and mesh with the gear 233 (Figs. 6, 7 and 8). The portion 333 of the sleeve 335 serves as a guard whereby the gear 332 may beheld out of mesh with the gear 233. A clamping or binding screw 331 passes through an elongated slot 333 formed in the hub portion of the arm 333 and is screw threaded into the sleeve 335. By tightening the screw 331 (Fig. 6), the sleeve 335 may be locked with respect to the arm 333. If it is desired to disconnect the incremental automatic down feed, the screw 331 is loosened and swung in a counterclockwise direction into the dotted line position 331 (Fig. 8), which movement swings the shield 333 of ward areuate movement of the lever 333 with a the gear 332 in mesh with the feed gear 233 the sleeve 335 so that it surrounds the operative portion of the gear 332 and thus holds it out of mesh with the feed gear 233. The screw 331 may be locked in this position to prevent downward incremental automatic feeding movement of the grinding wheel when desired.

The stud 33l passes through an arcuate slot (Figs. 5 and 9) formed in the apron 231- and is rotatably supported in a suitable bearing formed in the upper end of an arm 343 (Fig. 5). The arm 343 is keyed to a sleeve 3 which is in turn rotatably supported on a rotatable sleeve 342. The sleeve 342 is rotatably mounted on a stud 343 which is fixedly supported by the apron 231. The sleeve 342 is provided with an integral downwardly extending arm 244 which is connected by meansof a stud 345 (Fig. 5) to a link 343. The other end of the link 343 is connected by a stud 341 to one end of a piston rod 343 (Fig. 5). A piston 343 is formed integral with the other end of the piston rod 343. The piston 349 is slidably mounted within a fluid pressure cylinder 353 which is fixedly mounted within the apron 261. A tension spring 351 located outside the cylinder 353 is connected between a stud 332 fixedly mounted on the casing of the cylinder 353 and the stud 341. The tension spring 35l serves normally to maintain the arm 344 in position 344a. With the lever 344a in the position shown (Fig. 5), the stud 33! and its supporting arm 343 are positioned at the upper end of its stroke. I

When it is desired to impart a downward feeding movement to the grinding wheel 35 in timed relation with the cycle of operation, fluid under pressure is admitted through a pipe 353 into a cylinder chamber 354 (Fig. 5) to move the piston 343 toward the left, which movement serves to rock th arm 344 in a clockwise direction from position 344a into position 344 (Fig. 5), which movement rocks the arm 343 also in a clockwise which imparts arotary movement to the feed screw 253'so as to produce a downward feeding movement of the grinding wheel assembly.

In order to vary the extent of down feeding movement at each actuation of the feed arm 333, it is desirable to provide a suitable adjusting mechanism, whereby the effective strok of the arm 333 and gear 332 may be adjusted as desired. The sleeve 3 has an upwardly extending integral flanged portion 333 which has a graduated scale thereon (Fig. 5). The inner sleeve 342 is provided with a knob 333 at its outer end. The knob 333 is provided with a cut-out portion forming a substantially U-shaped crosssectional area 313 which serves as a support for a pair of opposed adjusting screws 31! and 312. The adjusting screws 31i and 312 are arranged to engage a stud 313 which projects from and is fixedly supported by the sleeve 3 and the graduated flange 333. It will be readily apparent from the foregoing disclosure (that by manipulation of the screws 3" and 312, the lever 344 may be adjusted relative to the arm 343 so as to vary the extent of swinging movement of the arm 343 and thereby vary the feeding movement of thearm 343 and thereby vary the feeding movement of the feed arm 333 and the gear 332. The arm 343 always moves up into engagement with the adjustable stop screw 333, thus limiting the up movement of the feed, arm 333 and the gear 332. The adjustment is facilitated by the opposed screws 3H and 312 and serves to adjust the arm 344 relative to the arm 343 so as, to shift the position of the piston 343 and thereby vary the length of stroke of the feed arm 333.

Automatic lift-grinding wheel shaft 335 which supports a single vane 38!.

' When fluid under pressure is admitted through a 35 into its starting position so that it is ready for the next grinding cycle. During the operative stroke of the motor 383, any fluid within the motor on the opposite side of the vane 33! may exhaust through a pipe 334 (Fig. 3) into the reservoir l25.

Manually Operable lift mechanism A manually operable lifting mechanism is provided for raising and lowering the grinding wheel slide assembly. Due to the massive, heavy wheel slide assembly, it is desirable to provide a manually operable mechanism which is arranged so that the wheel slide assembly may be raised and lowered without undue eifort on the part of the operator. The manually operable feed wheel 232 is utilized to rotate the feed screw 253. In order to provide an easily operated mechanism, the fluid motor 333 together with the control valve 313 are utilized to overcome part of the weight of the massive heavy wheel slide assembly. The

valve 318 is, operatively connected in a manner to be hereinafter described so that when the hand wheel 282 is rotated to cause a lifting movement of the grinding wheel 65, the valve 318 will be partially opened to admit a supply of fluid under pressure to the fluid motor 388, the fluid under pressure admitted to the motor 388 being such that the motor has not sufficient power-to rotate the feed screw 258 to lift the grinding wheel slide assembly. The mechanism. how- .slide, it being. unnecessary on the down move- 'ment.

A vertically extending lever 415 is provided with an enlarged hub portion 415 at its upper end which surrounds and is rotatably supported on a hub 411 formed integral with the gear 218 (Fig 3). A friction plate 418 also surounds the hub 411 and is interposed between the feed gear 288 and the hub portion 418 of the lever 415. A plurality of spaced pins 418 carried by the friction plate 418 engage radially extending slots 428 so that the friction plate 418 and hub portion 415 of the lever 415 will turn together with re spect to the supporting hub 411. A plurality of spring-pressed balls 421 are provided in a fixed part of the apron 281. The spring-pressed balls 421 engage the base of the friction plate 418 and hold it in frictional engagement with the feed gear 288 so that when the hand wheel 282 is rotated to rotate the feed gear 288 and transmit a rotary motion to the shaft 212 and the feed screw 258, a rotary motion will be imparted through th friction plate or disk 418 and the hub portion 418 to swing the lever 415 either in a clockwise or counterclockwise direction depending upon the direction of rotation of the hand wheel 282.

When the hand wheel 282 (Fig. 5) is rotated in a counterclockwise direction, th index wheel 288 moves the friction plate 418 and swings the lever 415 until its lower end contacts the stop screw 428. This occurs when the feed gear 288 is rotated manually or the arm 338 feeds the grinding wheel down, as the fluid motor 388 is not required to assist the lowering of the heavy wheel slide assembly, as gravity aids the operator and also the automatic wheel feeding mechanism. Consequently the key 324 engages its lost motion keyway on the right-hand side (Fig. 9) so that the gear 218 which mounts the key 324 will immediately feed the grinding wheel 85 down for another grinding pass or stock removal. In this case, the valve stem 311 is not moved and also there is no relative movement between the feed gear 288 and the gear 218. Consequently the spring 412 is not compressed but remains in a neutral position and the lever 415 is maintained in contact with the screw 428 during the feeding of the grinding wheel down at the end of the cross pass.

A substantially U-shaped bracket 424 is either formed integral with or fixedly mounted to the apron 281 and is provided with two upwardly extending spaced arms 425 and 426 which serve as supports for a pair of opposed adjustable stop screws 421 and 428. The stop screws 421 and .428 are arranged in the path of movement of .the lever 415 and serve to limit its movement either in a clockwise or counterclockwise direction.

In case the operator desires to manually raise the wheel slide assembly-at .the start of a grinding cycle to offset the amount of stock removal on the first cross pass of the. grinding wheel 85, the hand Wheel 282 is rotated clockwise. The feed gear 288, through the friction plate 418,

.will rock the lever 415 without rotating the gear 218 which would raise the heavy wheel slide assembly, requiring great exertion by the operator if a lost motion keyway was not used for mounting the key 324. This is accomplished by a keyway wider than the key 324 (Fig. 9). This lost motion is not taken up until the lever 415 strikes the screw 421 and has shifted the valve stem 311 so that the fluid motor 388 will act as a booster and assist the operator to raise the massive grinding wheel assembly.

In this movement of the lever 415, the gear 218 does not move but compresses a spring 412 (Fig. 9) mounted between a cut-out portion in the plate 413 pinned to the feed gear hub 219 by a pin 414 to a pin mounted in the gear 218. The operator adds his pressure to the pressure of the motor 388 and the wheel slide assembly will be raised as the hand wheel is kept rotating by the pressure of the operator. The friction plate 288 will slip but maintain the lever 415 in the operating position. When the hand wheel is stopped, the released tension of the spring 413 and the pendulum action of the lever 415 will return it to its central or neutral position provided the friction does not slip. The spring 315 will also assist this movement of the lever 415, also obtained when the vane motor 388 lifts the grinding wheel 65 at the end of the cycle. In this case the motor 388 furnishes the additional power required.

A stud 438 is adjustably supported adjacent to the lower end of the lever 415. The stud 438 is positioned in the path of movement of a pair of adjustable collars 431 (Fig. 9) which are screw threaded onto a threaded sleeve carried bythe valve stem 311. When "the hand wheel 282 is rotated in a clockwise direction (Fig. 5) to raise the wheel slide 58, the lever 415 will be moved also in a clockwise direction and the stud 438 engaging the adjustable collars 431 will shift the valve stem 311 toward the left a sufficient distance to open a port in the valve 318 so as to admit fluid under pressure to the motor 388. The power of the motor 388 in this position of the valve, however, is slightly less than that required to rotate the feed screw 258. The operator supplies the necessary additional power on the hand wheel 288 to impart a rotary movement to the feed screw 258 to raise the grinding wheel assembly to the required extent. As soon as the rotary movement of the hand wheel 288 is stopped, the released compression of the spring 315 will shift the valve 318 back to its neutral or central position, thus cutting off the flow of fluid under pressure to the fluid motor 388. By continuing the rotary movement of the hand wheel 288, the grinding wheel 65 maybe raised to the required extent.

If it is desired to lower the grinding wheel manually, the hand wheel 282 is rotated in a counterclockwise direction, which movement, through the friction plate 418, rocks the lever 415 so that its lower end engages the adjustable stop screw 428 (Fig. 9). This movement 2,302,915 of the lever does not shift the valve 8 and continued rotation of the hand wheel 282 through the gear mechanism previously described rotates the shaft 212 and this in turn through the gear mechanism previously described rotates the feed screw 258 to cause a lowering of the wheel slide 58 supporting the grinding wheel 65 to position the grinding wheel 65 manually as desired.

"-C'ross feed-wheel slide The transversely movable grinding wheel slide 58 is arranged so that it may be moved transversely by means of a. manually operable traversing or feeding mechanism or, if desired, the

- may be continuously moved transversely at a slow uniform rate during a grinding wheel operation.

Hand traverse The wheel slide 58 is provided with a rack bar 435 which extends lengthwise of the wheel slide. A gear 486 meshes with the rack bar 435 and is fixedly mounted on the end of a rotatable shaft 431. The shaft 431 is journalled in anti-friction bearings 438 and 438 which are supported by the vertically movable slide 48.

A large bevel gear 448 is keyed to the shaft 431. A bevel gear or pinion I is mounted at one end of a rotatable shaft 442 which is journalled in anti-friction bearings 443 and 444. The bearings 443 and 444 are supported in a slidably mounted sleeve 445 which is journalled in a suitable aperture within the vertical slide 48 (Fig. 13). The sleeve 445 is slidably keyed by means of a, key 446 to a bracket 454 fixedly mounted on the vertical slide 48, so that the sleeve 445 may be moved endwise but held against.

rotation. The-sleeve 445 may be positioned (Fig. 13) with the bevel pinion I out of mesh with the bevel gear 448 during a power traversing movement of the wheel slide 58. In case it is desired to traverse the wheel slide 58 manually, the sleeve 445 is moved toward the left (Fig.'13) to move the bevel pinion 44] into mesh with the bevel gear 448. The shaft 442 carries a member 441 to which is fixedly mounted a manually operable hand wheel 448, the member 441 and the hand wheel 448 being arranged to rotate together. When it is desired to traverse the wheel slide 58 manually, the hand wheel 448 is moved into dotted line position 448a which moves the sleeve 445 and the bevel gear I also toward the left (Fig. 13) to mesh the bevel pinion I with the bevel gear 448. Rotary movement of the hand wheel 448 will then transmit a comparatively fast traverse to the grinding wheel slide 58.

In case it is desired to produce a relatively slow transverse movement of the grinding wheel slide 58 under manual control, a locking pin 449 is provided. The locking pin 449 (Fig. 13) is carried by the hand wheel 448 and member 441 and is arranged to engage any one of a series of notches 458 formed in the bracket 454 which is fixedly supported on the vertical slide 48, thereby locking the hand wheel 448 against rotation.

A speed reducing unit 45! (Fig. 13) is fixedly wheel 448. This speed reduction unit has not been shown in detail since this reduction unit is the well known "Heliocentric speed reduction unit manufactured by Universal Gear Corporation of Indianapolis, Indiana. A hand-wheel 452 is mounted on a drive shaft 453 of the speed reduction unit 45l. When the hand wheel 488 is locked by the locking pin 449 against rotary movement and the hand wheel 452 is rotated, a relatively slow rotary movement is transmitted by the speed reduction unit 45l to move the wheel slide 58 transversely at a slow uniform truing speed. The diamond is held by the diamond holder which is adjustably mounted in a truing attachment unit 465 fixedly mounted on the vertlcal slide 48 (Fig. 1). Such a traversing movement is desirable in case it is desired to true the grinding wheel 65 manually.

Hydraulic traverse-wheel slide The wheel slide 58 is preferably moved transversely during the automatic grinding cycle and also during a truing operation by means of a hydraulically operated mechanism comprising a fluid pressure cylinder 455 which is fixedly mounted on the vertically movable slide 48 (Fig. A piston 456 is slidably mounted within the cylinder 455 and is connected to the central portion of a double end piston rod 451. The rod 451 is connected by means of a, bracket 458 to the wheel slide 58. The bracket 458 is either fixedly mounted on or formed integral with the wheel slide 58. Fluid under pressure from the pump I35 previously described passes through a pipe 459 (Fig. 2) to a pilot valve 468 and also to an automatic wheel slide traverse control valve 46!, both valves being attached to a bracket 466 which is fixedly mounted to the vertical slide 48. A selector valve 462' is provided for controlling the hydraulic. operation of the wheel slide 58. The selector valve 462 is a rotary type valve controlled by a manually operable dial 463 which is mounted adjacent to the front of the vertical slide 48. The dial 463 may be rotated to any one of three positions. An index point 464 is provided to facilitate location of the dial 463 in the desired operating position.

The selector valve 462 (Fig. 2) has been shown diagrammatically in the three operating posimounted within an integral hub of the hand tions, only one of which is connected in full lines with the main piping of the machine. The selector valve 462 (Fig. 2) is connected in full lines with the piping diagram, and is shown in position for an automatic incremental cross feeding movement in timed relation with the reciprocatory movement of the work table 4|. The selector valve 462 is also shown in position 462a (Fig. 2), in which position the valve is positioned so that fluid may by-pass from one end of the cylinder 455 to the other end thereof to allow free unrestrained movement of the wheel slide 58 under the influence of the manually operable traverse hand wheels 448 and 452, respectively. The valve 462 is also shown in position 462D (Fig. 2) which is in a truing position to be hereinafter described.

For fine adjustments of the speed and amount for cross feeding a screw 485 is threaded in the bracket 466 which positions the dial 463. The dial 463 has an integral abutment on the projection 486 (Fig. 2) which strikes the screw 485, thereby locating the valve stem 58'! of the selector valve 462 in the desired relationship with the v-ports. The V-ports are connected with the exhaust pipe 5l5 leading to the valve 5H, in this way controlling the amount the grinding wheel 65 may be fed for the next grinding pass. An adjusting screw 481 positions the projection 486 of the dial 463 which in turn positions the valve stem 561 for a desired truing speed of the grinding wheel 65 across the truing unit 465. The shape of the truing exhaust ports in the sleeve of the selector valve 462 is shown in Fig. 38.

The reversing valve 461 is a piston type reversing valve comprising a valve stem 413 having formed integrally therewith a plurality of valve pistons. The reversing valve 461 serves to admit fluid under pressure either through a pipe 414 or a pipe 415 into cylinder chambers 416 or 411 of the cylinder 455 to produce a longitudinal movement of the piston 456 and the wheel slide The valve stem 413 is provided with a cam 418 at its right-hand end (Fig. 2). When the valve stem 413 together with the cam 418 is moved toward the right (Fig. 2), the cam 418 serves to open a normally closed limit switch 419 and simultaneously to close a normally open limit switch 486 mounted on the bracket 466. During the movement of the valve stem 413 toward the right (Fig. 2), a pivotally mounted detent 481 carried by the valve stem 413 rides idly over the actuating plunger of a normally open limit switch 482. When the valve is moved toward the left (Fig. 2), the detent 481 actuates the plunger and closes the limit switch 482. The limit switches 419, 480 and 482 are electrically interconnected with the other mechanisms of the machine in a manner to be hereinafter described.

An automatic reversing mechanism is provided for shifting the pilot valve stem 468. The shaft 431 is provided with a reduced extension 488 which supports at its right-hand end a spiral gear 489 which meshes with a spiral gear 496. The spiral gear 490 is mounted on the right-hand end of a shaft 491 which is journalled in bearings 492 and 493, respectively, which are in turn supported in the bracket 466 mounted on the vertically movable slide 48. A reversing plate 494 is mounted on the left-hand end of the shaft 491. The plate 494 is provided with a T-shaped annular groov 495 extending around the plate 494 adjacent to its periphery. A pair of reversing dogs 496 and 491 are adjustably supported by means of the T-slot 495. A graduated dial scale r 498 is provided to facilitate positioning of the reversing dogs 496 and 491. For convenience in this positioning movement, the graduations of the scale 498, as illustrated, are in inches per distance of cross traverse of the grinding wheel Fluid exhausting from either end of the cylinder 455 passes through one of the chambers in the wheel slide reversing valve 461 and passes out through the selector control valve 462 and through a pipe 515 and a traverse valve 511 mounted on the vertical slide 48 (Fig. 10) and which is actuated by a push type solenoid 518. In the position of the parts (Fig. 2) fluid under pressure passing through the pipe 515, the valve 511, and through a pipe 519, exhausts into the reservoir 125, thus allowing exhaust of fluid at a controlled rate of speed. An adjustable relief valve 516 connected to a pipe 514 allows fluid to exhaust from the cylinder 455 through the pipe 515 when the solenoid 518 is released. This serves to close the valve 511 to prevent vibrating the wheel slide 56 when it is suddenly stopped. The rapid cross feed of the grinding wheel 65 is obtained by energizing the solenoid 518 to open the valve 511 so as to allow unrestricted passage 518 is energized determines the extent of cross feed of the wheel slide 56.

Operation The operation of the improved surface grinding machine will be readily apparent from the foregoing disclosure, assuming all of the adjustments of the various mechanisms to have been previously made and the machine to be set up for grinding a predetermined work piece to the required extent. A selector switch 525 is positioned for an automatic cycle. A switch 526 is closed to start the pump drive motor 521. A push button 528 is actuated to start the wheel drive motor 68.

A work piece 529 is then positioned on the work table 41 when the table 41 is in its extreme left-hand position (Fig. 1). The start and stop lever 215 is then shifted in a clockwise direction into position 215a to move the start and stop valve 205. The shifting of the start and stop valve 265 toward the left (Fig. 2) serves to allow fluid to exhaust from cylinder chamber 114 in cylinder 106 and thereby allow the pressure passing through pipe 111 into the cylinder chamber 112 to start the table 41 traversing toward the right (Fig. 1).

When the start and stop valve stem 2116 is moved toward the left to start a grinding cycle. the cam 229 (Fig. 2) closes the normally open limit switch 230 which serves to render the electrical cycle timer or counter 231 operative and at the same time energizes the solenoid 181 which produces a downward movement of the roller 148 to shift it downwardly to position 148a into the path of the cam 162 on the table dog 163. At the same time the solenoid 181 is energized, a normally open electrical relay 5311 (Fig. 2) is energized to close a circuit connected with the normally open switch 531 (Fig. 3). The traverse of the table 41 toward the right con tinues until the roller 141 engages the cam 156 on the table dog 161, and continued movement of the table 41 serves through the shaft 149 and lever 165 to start a reverse movement of the reversing valve 116. During the shifting movement of the reverse valve a cam 532 carried by the rod 161 closes the normally open limit switch 531. The limit switch 531 operates through the relay 536 and the limit switch 419 to actuate the relay 522. The closing of the relay 522 serves to energize the solenoid 518 which shifts the valve 511 upwardly to allow exhaust of fluid from the wheel slide cylinder chamber 411 and pipe 415, thereby permitting the fluid under pressure from passing through the pipe 414 into the cylinder chamber 416 to move the piston 456 toward the right (Fig. 2) so as to feed the wheel slide 50 and the grinding wheel 65 toward the right so that on the next traverse of the work table 41, the grinding wheel 65 will grind a fresh path across the face of the work piece 529. The solenoid 518 is only energized instantaneously while the cam 532 passes over the plunger of the limit switch 531, after which the solenoid 518 is deenergized and the valve 511 moved downwardly to stop the cross feeding movement of the grinding wheel 65. The reversing valve completes its reversal by the influence of fluid under pressure in a manner similar to that described in the prior U. S. patent to W. H. Wood, No. 2,071,- 677 dated February 23; 1937. The cycle just described is continued until the grinding wheel 65 has successively ground paths across the entire face of the work piece 529.

During'the cross feeding movement of the grinding wheel 65 and its supporting wheel slide 50, the reversing plate 494 moves intermittently in a counterclockwise direction (Fig. 2) until the dog 491 engages the detent 503 to rock the reversing' lever 500 in a counterclockwise direction, which movement shifts the pilot valve 480 toward the right (Fig. 2) to admit fluid under pressure from the pipe 459 through the pipe 412 to shift the wheel slide reversing valve 46I toward'the right (Fig. 2) to reverse the direction of movement of fluid to and from the cylinder 455.

During the shifting movement of the wheel slide reversing valve 46I toward the right, the cam 418 carried by the valve stem 413 closes the limit switch 480 which serves to close a circuit and energize the solenoid 534 to shift the valve 535 (Fig, 3) upwardly. The upward movement 5 of the valve 535 admits fluid under pressure grinding wheel across the operative face of the work piece 529. The table continues its reciprocatory movement and the grinding wheel 65 is traversed transversely toward the left by intermittent successive increments until the grinding wheel 65 again reaches the position illustrated, thus completing the second pass of the grinding wheel 65 across the face of the work piece 529 being ground.

During this movement of the wheel slide 50 and grinding .wheel 65 toward the left, the re-.-

versing plate 494 moves in a clockwise direction until the dog 496 engages the detent 503 to rock the reversing lever 500 in a clockwise direction to again shift the pilot valve 460 into the position shown in Fig. 2. This movement of the pilot valve 480 reverses the direction of flow of fluid so that fluid passes through the pipe "I to move the reversing valve 46I toward. the left into the position illustrated in Fig. 2. During the movement of the reversing valve 46] toward the left, the detent 48I engages and closes the limit switch 482 which is connected to the time cycle counter 23I to give the timer an impulse,

After a predetermined number of complete reciprocations of the grinding wheel across the face of the work piece 529 which is being ground during the continuous reciprocation of the work table 4| a corresponding number of impulses is imparted to the cycle counter 23I, after which the counter 23I deenergizes the solenoid I81 and the relay 530 to release the tension of the spring I93, thus shifting the roller I48 upwardly out of the path of the cam I62 on the dog I 63, so

that the table 4I will travel to'its extreme lefthand or loading position. In this position of the roller I48, the roller engages a cam I60 onlthe the left (Fig. 1) for the start of the next cycle,

thus ending one complete grinding cycle. At the same time, the dog I6I rocks the control lever 2 I 5 into the position 2I5a, thereby shifting the stop and start valve 205 to stop the table U in a loading position. The time cycle counter 23I may be set as desired so that, depending upon the amount of stock desired to be removed from the work piece 529, the grinding wheel 65 may be fed downwardly and traversed intermittently by successive increments across the work face a predetermined number of times, after which the machine automatically stops without attention on the part of the operator. 7

Shifting of the stop and start valve 205 into the position shown in Fig. 2 opens a port to admit fluid under pressure through the pipe 382 into the fluid motor chamber 383 to cause the vane 38I of the motor 380 to rotate in a counterclockwise direction. Thi movement serves through the gears 390 and 39I to rotate the gear 211 to transmit a rotary movement through the mechanism previously described to rotate the vertical feed screw 250 in the reverse direction automatically to return the grinding wheel into its initial position so that it is ready for the next grinding cycle. At the start of the grinding cycle when the stop and start valve 205 -is shifted toward the left (Fig. 2), the fluid within the fluid vane motor chamber 383 is opened to the exhaust, thus releasing the tension of the spring 386 which rotates the vane 38I in a clockwise direction (Fig. 2) to reset the motor 380 ready for the end of the next cycle.

If for any reason it is desired to control the cycle of operation manually instead of automatically, the selector switch 525 is shifted to a hand position, in which position the table 4I may be reciprocated under manual control and the wheel slide 50 may be traversed also under the manual control of the operator.

When the selector switch 525 is turned to a hand" position, the cycle timing counter 53I is rendered inoperative. The relay 530 is energized and the solenoid I81 deenergized so that the wheel slide 50 is automatically fed across the work by means of the cam 532 closing the limit switch 53I. When the machine is under "hand control, the grinding cycle may be stopped by unlocking the stud I98 in the slot 200 and lifting the stud I98 to raise the roller I48 out of the path of the cam I62 on the dog I63 so as to allow the table 4| to move to its left-hand or loading position.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together .withmany thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbeforeset forth or shown in the accompanying drawings-is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. In a grinding machine having a base, a longitudinally movable work table thereon, a rotatable grinding wheel, a vertically movable slide for said wheel which is movable vertically relative to said base, a nut and screw mechanism to move said slide vertically, a fluid pressure system including a fluid motor, operative driving connections between the motor and said screw, said motor and driving connections being arranged so that the power transmitted to the slide is slightly less than that required to move the slide, and a manually operable traversing mechanism including a hand wheel which is operatively connected when rotated in one'direction to rendersaid fluid motor operative so that the additional power required to move the slide manually may be supplied to raise said slide.

2. In a grinding machine having a base, alongitudinally reciprocable work table, a rotatable grinding wheel, a vertically movable slide supported on said base, a nut and screw mechanism operatively connected to move said slide vertically relative to said base, a manually operable traversing mechanism including a rotatable hand wheel operatively connectedtorotate said screw, a fluid pressure system including a fluid motor, operative driving connections between the motor and the screw, a valve to control the admission to and exhaust oi fluid from said motor, means normallyto hold said valve in' a closed position, and frictional connections between said manually operable hand wheel and said valve whereby rotation of said hand wheel in one direction serves to actuate said valve to start said motor so that the motor serves to supplement the manual traverse mechanism to provide an easily operated manual left for the slide.

3. Inagrindingmachinehavingabase.alongitudinally reciprocable work table, a rotatable grinding wheel, a vertically movable slide for said grinding wheel which is movable vertically relative to said base, a nut and screw mechanism to move said slide, a manually operable traverse mechanism to feed said slide vertically toward and from said table including a rotatable hand wheel which is operatively connected to rotate said screw, a fluid pressure system including a fluid motor, operative driving connections between the motor and screw, a control valve to control the admission to and exhaust or fluid from the motor, a spring nor'mailyto maintain said valve in an inoperative position, and trictional connections between said hand wheel and said valve whereby the valve is actuated when the hand wheel is rotated in one direction to cause a vertical upward movement of the slide to start said motor so that the motor supple- 1 ments the manual rotation of the hand wheel to provide an easily operated mechanism to raise 

